1. Field of the Invention
The invention relates to a pirate-proof optical recording disc and to a process for reading such a disc. The invention can in particular be applied to CD or DVD format optical discs but it also extends to any other format.
2. Discussion of the Background
Owing to the appearance on the market of low-cost CD type recorders (CD-R or CD-RW and soon DVD burners), duplication, especially of CD-ROMs or DVD-ROMs, has become or will become accessible to semi-professionals or to amateurs. It is therefore very important for publishers, in particular publishers of software or of games, to protect themselves against the pirating of their information, especially if such pirating is on an industrial scale.
There are already a few systems which make the copying of data and/or their use more difficult. These systems are in particular based on encryption techniques. However, their effectiveness is limited since, with the computer means available to potential pirates, the xe2x80x9chackingxe2x80x9d of these systems is far from impossible.
The subject of the invention is a pirate-proof disc and a method of reading barring unauthorized use of the datum stored and in particular the use of pirate copies by virtue of the use of a disc having a specific physical configuration. The disc of the invention can be read by a conventional reader, without modification. However, its structure renders any copy made by easily accessible means unusable and the structure of the disc cannot be simulated. Moreover, the reproduction of such a disc cannot be done without very sophisticated and extremely expensive industrial means.
According to the invention, there is provided an optical data recording disc comprising a continuous main recording track recorded in a known general manner in the form of a spiral comprising a plurality of successive turns, characterized in that the disc comprises, furthermore, at least one secondary track span interposed between two adjacent spiral turns, the said span carrying at least one identification datum specific to the said span, a first datum regarding the pirate-proof nature of the disc and a second datum regarding the positioning of the secondary track span with respect to the main track, the said first and second data being arranged in a zone for initializing the reading of the disc on the main track.
According to another aspect of the invention, there is provided a process for reading the above disc, characterized in that it comprises the steps of:
a) reading the data arranged on the main track in the said initialization zone;
b) checking that the physical structure of the disc complies with that described by the data of the initialization zone;
c) authorizing the use of the data carried by the main track and the operation of the corresponding application only when the result of the check step b) is positive.